1. Field of the Invention
This invention relates to a machine bolt or screw which when implanted will automatically prevent stripping or damaging of engaged threaded parts and will, after installation, become and remain tamper-proof. More specifically it relates to a double-headed machine screw or bolt, one slotted, shaped or socketed head located above a tapered head.
Still more specifically, it relates to a double-headed machine screw or bolt, which when torqued to its maximum tightness, will cause the slotted head to automatically shear and break free at the narrow neck, at a desired and predetermined force (pounds per square inch), to preclude damaging the engaged screw threads. This auto-torque function will be accomplished during its manufacturing process. The breaking point of the narrow neck will be accomplished by three design factors: (1) The strength of the material from which the screw or bolt is made; (2) The diameter (thickness) of the narrow neck; (3) The predetermined amount of torque required to shear the narrow neck prior to causing damage to the engaged threaded parts, thereby automatically self-torquing its objective and in turn, eliminating the need for torque wrenches, slip-type ratchet tools or slip-clutch power tools. Thus the basis for the "Auto-Torque" portion of the two-part title of this invention.
Still, and even more specifically, it relates to a double-headed screw or bolt, which when more than the required torque is applied to position it tightly in place, will shear the narrow neck between the slotted and tapered heads, leaving a tamper-proof fastener securely in place, having no gripping surface or configuration to facilitate its removal.
2. State of the Prior Art
Manufacturing requirements, and the needs of these times, have dictated the need for a screw-type fastener that, when installed, cannot be over-tightened, thus preventing damage to pertinent threaded parts and, after being installed, cannot be removed in the usual manner, thus rendering it self-torquing and tamper-proof.
During prosecution of the parent application a number of references were cited to show related devices. These include Bissell U.S. Pat. No. 1,243,799; British Patent No. 1,437,383; and German Patents Nos. 2,353,751; 2,519,854 and primarily 3,738,409. German Patent No. 3,738,409 (Meyer) was relied on for rejection. However none of the patents, including Meyer, show the sharp conical angle of applicant's device which makes it impossible to gain a gripping surface. Still further, none of the patents cited as related devices have the additional automatic, self-torquing function that prevents over-tightening and precludes the possibility of damaging the pertinent threaded parts.